Modern undersea armored cable systems sometimes require the connection of a torque-balanced section to one that is not torque-balanced. An example of such a transition is the connection of a medium armor (MA) non torque-balanced cable to a light armor (LA) torque-balanced cable.
During the deployment of such transitions, considerable stress can be generated by the heavier, non-torque balanced section and imparted through the junction into the lighter torque-balanced section. This stress is manifested as the transition travels on board ship over the cable engine drum and moves toward the overboarding sheave. As the junction first leaves the cable engine drum, the full value of torque existing in the higher torqued medium armor cable will be imparted directly to the torque-balanced light armor cable and must be absorbed over an extremely short lenth of cable. The latter is thereby caused to rotate beyond its acceptable torsional strain limit.
Depending on the structural differences between the two cable sections and the axial load momentarily incident at the cable transition, the torque-induced rotation can be substantial. For example, in this particular MA/LA transition rotations in excess of 400 degrees can occur. The resultant stress in the lower torqued, less torsionally rigid cable, can be substantial because this torque-induced rotation takes place over a very short length of the less resistant cable as it disengages from the cable engine drum. Permanent and possibly undetected strain damage can easily result, which undermines the structural and functional integrity of the entire cable system.
Accordingly, one object of the invention is to provide a transition device that allows deployment of cable systems comprising sections of differing torsional rigidities and structures from a cable tank into the ocean, with decreased risk of twist damage due to sudden torque-induced rotation.
A further object of the invention is to allow the deployment of an ocean cable consisting of sections having differing armor layers while avoiding the risk of twist damage due to sudden torque-induced rotation.
An additional object of the invention is to allow rapid and positive application of a torque restraining device, either at the cable manufacturing factory prior to shipment, or on board ship just prior to deployment.
A specific object of the invention is to permit spreading or distribution of torque-induced rotation over a substantial length of a less resistant cable section.